As is well known and understood, adequate dilation of the pupil of the eye is essential during cataract and posterior segment surgery. As is also understood, situations exist where the pupil cannot dilate adequately. For example, where there has been a prior surgical intervention, or where the eye has been traumatized, or where there exists a physiological reaction to a manipulation, various methods have been suggested to provide an adequate pupillary opening.
The simplest method involves the use of pharmaceuticals--but, in a significant number of patients, this arrangement often proves ineffective, and sometimes is associated with producing a toxicity to the cornea. A second method for enlarging the pupil is for the surgeon to excise a small wedge of the iris in an attempt to create an adequate pupillary aperture; however, such procedure (termed an "iridectomy") tends to produce an eccentric dilation--rather than a uniform one--and, additionally, releases pigment cells (because of the severance of the iris) which is preferable to avoid. A third method--i.e. mechanical dilation through a retraction of the iris by means of sutures passed through the scleral wall--has been noted to be delicate, time-consuming and awkward to accomplish.